132 MUSCLE. 



stance diminishes in quantity, the muscular fibres lie closer 

 together, and have a more intensely white appearance upon 

 the black ground. When some of this transparent substance, 

 taken from a foetus of the size before mentioned (and in order 

 to exclude as completely as possible the embryonal cellular 

 tissue which surrounds the entire muscle, a portion should be 

 cut out from the centre of the muscle), is examined with a 

 magnifying power of 450, it exhibits various kinds of granules 

 differing in size, and lying in a finely granulous mass. On 

 examining these granules more accurately, they are found to 

 vary, both in size and appearance, being round or oval, more 

 or less opaque or transparent. A great many of them may be 

 recognized as cell-nuclei by their form. In many instances, 

 even when they are still connected together, the granulous 

 substance around them is more or less distinctly seen to have 

 a defined globular figure, within which the nucleus lies. This 

 is, however, observed most distinctly when any of the granules 

 become separated from the transparent substance, and float 

 about in the fluid upon the object-glass. A quantity of globules 

 are then seen floating about isolated, each one containing the 

 characteristic cell-nucleus, which is placed eccentrical, varies 

 much as to its size, and is often furnished with nucleoli. (See 

 pi. Ill, fig. 13.) We are already familiar with this as the 

 rudimentary form of most cells. The finely granulous por- 

 tion of the transparent mass is formed, in part, of the bodies of 

 the cells, which, when in close contact, are difficult to distin- 

 guish, and in part, of the cytoblastema in which the cells have 

 been generated. Some of these cells which float about are 

 becoming elongated into fibres, which are manifestly those of 

 areolar tissue. Such instances, however, are rare, and these 

 cells seem to be something quite peculiar. They might be re- 

 garded as the primitive cells of new muscular fibres ; but from 

 the manner in which Valentin expresses himself, one should 

 infer that they are formed at a later period, for he says, 

 " masses of globules begin to accumulate between the mus- 

 cular fasciculi from the period at which they become trans- 

 parent j* it is clear that he here refers to the nuclei of these 

 cells. This must, therefore, remain an undecided point. 



We next examine the muscular fibres (primitive fasciculi) 

 in the dorsal muscles of the same foetus. Thev do not all 



